1. Field of the Invention
This invention relates to an apparatus for receiving thermoplastic and other hot melt materials and adhesives, melting the material, and supplying the melted material to a dispenser. Heat is supplied to the material in a carefully controlled manner through a series of multiple heat sources so as to ensure rapid and even heating and subsequent melting of the material.
2. Description of the Related Art
In the past, hot melt materials were converted from a solid or quasi-solid state to a flowable melted state by placing the unmelted material in a container having heated walls, whereby heat would travel from the wall, first through the material closest to the wall, and eventually to the center region, thereby melting all of the material. This system suffered certain drawbacks, in that the material closest to the walls was exposed to an excess of heat, thereby degrading or harming the material. Also, the time required to melt the entire batch of material was unsatisfactorily long.
Improvements in the form of grid type melters, whereby the material was melted in a heated grid, travelling then to a holding reservoir, for supplying to a dispenser, solved some of the problems experienced in the heated wall container type melters. However, these grid type melters also suffered certain drawbacks, in that the heat supplied to the material was uneven, resulting in the same and similar problems experienced in the previous devices. Generally, these prior art devices lacked the means by which heat may be transferred evenly to heat conducting surfaces contacting the material to be melted. Specifically, the prior art melters generally exhibit heating sources and elements which are at right angles to the heat exchange surfaces or fins. Also, the prior art utilizes heating sources which generally lie in a single plane at the base of the heat exchange element, and do not disclose heating sources provided at locations in the heat exchange element in such a manner that the heat exchange surfaces are all maintained within relatively close temperature ranges. The problems associated with uneven temperature distributions along heating surfaces in grid type melters have not been addressed or solved in the prior art.
It is therefore an object of the present invention to provide an improved grid type melter which addresses and solves the problems associated with uneven heating of materials to be melted. Specifically, the present invention provides a system for maintaining the heat exchange surfaces of a melter within a relatively narrow temperature range. The shape of the heat exchange surfaces of the present invention are arranged in such a manner that the material to be melted is exposed to relatively large heat exchange surfaces, in aggregate. The results are that the material is more evenly and rapidly melted, thereby maintaining the integrity of the material, and optimizing the flow of the material through the melter.